1. Field of Inventions
This application relates to polyethylene compositions, preferably blended compositions that include two or more different polyethylene polymers. Preferably, each of the individual polymers has a different complexity of long chain branching. The blend composition is preferably substantially linear, while at least one of the individual polymers is preferably branched, e.g., having an average long chain branching index of 0.85 or less.
2. Description of Related Art
Others have made compositions that include polyethylene, and reported various properties of those compositions. The technical literature is replete with such information, including the following articles: D. L. Cooke and T. Tikuisis, Addition of Branched Molecules and HMW Molecules to Improve Optical Properties of LLDPE (ANTEC, p. 22 (1989)); A. M. Sukhadia, The effects of Molecular Structure, Rheology, Morphology and Orientation on PE blown film properties (ANTEC, p 160 (1998)); F. C. Stehling, C. S. Speed, and L. Westerman, Macromolecules, 14, 698, (1981); A. M. Sukhadia, D. C. Rohlfing, M. B. Johnson, G. L. Wilkes, Journal of Applied Polymer Science, 85, 2396-2411, (2002); M. B. Johnson, G. L. Wilkes, A. M. Sukhadia, D. C. Rohlfing, Journal of Applied Polymer Science, 77, 2845-2864, (2002); E. Andreassen, and A. Larsen, Polymer Engineering and Science, 42, 1082-1097, (2002); and A. Prasad, R. Shroff, S. Rane, G. Beaucage, Polymer, 42, 3103-3113, (2001). Patents discussing compositions that include polyethylene include U.S. Pat. Nos. 6,388,017 and 5,258,449.
Efforts to improve polyethylene compositions, particularly compositions for films, have included attempts to make polyethylene with good optical properties, such as haze, and strength properties, such as Dart Impact. At least one shortcoming of many polyethylene compositions is that improved haze levels at a given film stiffness tend to be accompanied by loss in Dart Impact and/or other strength properties. There is a need at this time for polyethylene compositions that have a particular combination of desirable properties and characteristics. Those compositions are described below.